This invention relates to a solenoid-operated, pilot-controlled control valve.
Typically, hydraulically coupled (2-stage) valves require a flow induced pressure drop across the pilot stage in order to overcome seal drag and spring bias on the main valve stage to cause the main valve stage to open. One application for such valves would be as a control valve to control the raising and lowering of a conventional agricultural tractor hitch via a large area hydraulic cylinder. However, when such a hitch is not carrying any weight, a low pressure, low flow condition can arise wherein the flow would be insufficient to produce the pressure drop required for proper operation of the control valve.